From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30384 invoked by alias); 28 Jun 2018 16:37:00 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 30374 invoked by uid 89); 28 Jun 2018 16:36:59 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-25.6 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mx1.redhat.com Received: from mx3-rdu2.redhat.com (HELO mx1.redhat.com) (66.187.233.73) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 28 Jun 2018 16:36:57 +0000 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A7355DC3E for ; Thu, 28 Jun 2018 16:36:55 +0000 (UTC) Received: from localhost (unused-10-15-17-196.yyz.redhat.com [10.15.17.196]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8947220389E0; Thu, 28 Jun 2018 16:36:55 +0000 (UTC) From: Sergio Durigan Junior To: Pedro Alves Cc: gdb-patches@sourceware.org Subject: Re: [pushed] Fix follow-exec regression / crash (Re: Possible regression on gdb.multi/multi-arch-exec.exp) References: <20180607180704.3991-1-palves@redhat.com> <87in649jtd.fsf@redhat.com> <91c04ab2-ccbe-37ce-4a63-3350442dd406@redhat.com> Date: Thu, 28 Jun 2018 16:37:00 -0000 In-Reply-To: (Pedro Alves's message of "Thu, 28 Jun 2018 17:02:10 +0100") Message-ID: <87d0wa7tqw.fsf@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-IsSubscribed: yes X-SW-Source: 2018-06/txt/msg00690.txt.bz2 On Thursday, June 28 2018, Pedro Alves wrote: > On 06/28/2018 01:09 PM, Pedro Alves wrote: > >> I think the "gdb: Eliminate the 'stop_pc' global" patch >> () >> will fix this, because it moves the stop_pc assignment until >> after ecs->event_thread is refreshed: > I've split that bit out of that patch and pushed it in now, > as below. > > Thanks for reporting. I recall moving the stop_pc bit in the > multi-target branch a while ago after running into this crash, but when > splitting up the "Use thread_info and inferior pointers more throughout" > patch, I didn't realize that bit was needed as well. Thanks, Pedro. > From ecdc3a72c89e43e0e13c5478723b4f70b3964e9f Mon Sep 17 00:00:00 2001 > From: Pedro Alves > Date: Thu, 28 Jun 2018 16:57:18 +0100 > Subject: [PATCH] Fix follow-exec regression / crash > > After commit 00431a78b28f ("Use thread_info and inferior pointers more > throughout"), following an exec can result in gdb crashing. On some > systems, this is visible with gdb.multi/multi-arch-exec.exp and > gdb.base/foll-exec-mode.exp. E.g.: > > $ make check TESTS="gdb.multi/multi-arch-exec.exp gdb.base/foll-exec-mode.exp" > [snip] > FAIL: gdb.multi/multi-arch-exec.exp: first_arch=1: selected_thread=1: follow_exec_mode=new: continue across exec that changes architecture (GDB internal error) > ERROR: : spawn id exp10 not open > while executing > > Running multi-arch-exec under Valgrind we easily spot the problem: > > process 16305 is executing new program: ..../gdb.multi/multi-arch-exec/1-multi-arch-exec-hello > [New inferior 2 (process 0)] > [New process 16305] > ==16129== Invalid read of size 8 > ==16129== at 0x7FA14D: get_thread_regcache(thread_info*) (regcache.c:399) > ==16129== by 0x75E54B: handle_inferior_event_1(execution_control_state*) (infrun.c:5292) > ==16129== by 0x75E82D: handle_inferior_event(execution_control_state*) (infrun.c:5382) > ==16129== by 0x75BC6A: fetch_inferior_event(void*) (infrun.c:3918) > ==16129== by 0x748DA3: inferior_event_handler(inferior_event_type, void*) (inf-loop.c:43) > ==16129== by 0x464B5D: handle_target_event(int, void*) (linux-nat.c:4359) > ==16129== by 0x7047E0: handle_file_event(file_handler*, int) (event-loop.c:733) > ==16129== by 0x704D83: gdb_wait_for_event(int) (event-loop.c:859) > ==16129== by 0x703BF6: gdb_do_one_event() (event-loop.c:322) > ==16129== by 0x703CA2: start_event_loop() (event-loop.c:371) > ==16129== by 0x791D95: captured_command_loop() (main.c:330) > ==16129== by 0x79311C: captured_main(void*) (main.c:1157) > ==16129== Address 0x15a5bad0 is 32 bytes inside a block of size 600 free'd > ==16129== at 0x4C2E1E8: operator delete(void*) (vg_replace_malloc.c:576) > ==16129== by 0x8A15D0: delete_thread_1(thread_info*, bool) (thread.c:465) > ==16129== by 0x8A15FA: delete_thread(thread_info*) (thread.c:476) > ==16129== by 0x8A0D43: add_thread_silent(ptid_t) (thread.c:291) > ==16129== by 0x8A0DF0: add_thread_with_info(ptid_t, private_thread_info*) (thread.c:317) > ==16129== by 0x8A0E79: add_thread(ptid_t) (thread.c:331) > ==16129== by 0x75764C: follow_exec(ptid_t, char*) (infrun.c:1233) > ==16129== by 0x75E534: handle_inferior_event_1(execution_control_state*) (infrun.c:5290) > ==16129== by 0x75E82D: handle_inferior_event(execution_control_state*) (infrun.c:5382) > ==16129== by 0x75BC6A: fetch_inferior_event(void*) (infrun.c:3918) > ==16129== by 0x748DA3: inferior_event_handler(inferior_event_type, void*) (inf-loop.c:43) > ==16129== by 0x464B5D: handle_target_event(int, void*) (linux-nat.c:4359) > > The problem is that handle_inferior_event_1 is reading the stop_pc off > of a thread that was deleted by follow_exec. Before commit > 00431a78b28f, we didn't crash because we were passing down a ptid to > get_thread_regcache instead of ecs->event_thread. > > Fix this by simply moving the stop_pc reading until after > ecs->event_thread is refreshed. > > gdb/ChangeLog: > 2018-06-28 Pedro Alves > > * infrun.c (handle_inferior_event_1) : > Moving fetching stop_pc until after ecs->event_thread is refreshed. > --- > gdb/ChangeLog | 5 +++++ > gdb/infrun.c | 4 ++-- > 2 files changed, 7 insertions(+), 2 deletions(-) > > diff --git a/gdb/ChangeLog b/gdb/ChangeLog > index 81fae4924a..417c563849 100644 > --- a/gdb/ChangeLog > +++ b/gdb/ChangeLog > @@ -1,3 +1,8 @@ > +2018-06-28 Pedro Alves > + > + * infrun.c (handle_inferior_event_1) : > + Moving fetching stop_pc until after ecs->event_thread is refreshed. > + > 2018-06-28 Tom Tromey > > * coffread.c (coff_symfile_finish): Update. > diff --git a/gdb/infrun.c b/gdb/infrun.c > index 9548f9cafd..4c732340d1 100644 > --- a/gdb/infrun.c > +++ b/gdb/infrun.c > @@ -5289,13 +5289,13 @@ Cannot fill $_exitsignal with the correct signal number.\n")); > stop. */ > follow_exec (inferior_ptid, ecs->ws.value.execd_pathname); > > - stop_pc = regcache_read_pc (get_thread_regcache (ecs->event_thread)); > - > /* In follow_exec we may have deleted the original thread and > created a new one. Make sure that the event thread is the > execd thread for that case (this is a nop otherwise). */ > ecs->event_thread = inferior_thread (); > > + stop_pc = regcache_read_pc (get_thread_regcache (ecs->event_thread)); > + > ecs->event_thread->control.stop_bpstat > = bpstat_stop_status (get_current_regcache ()->aspace (), > stop_pc, ecs->event_thread, &ecs->ws); > -- > 2.14.4 -- Sergio GPG key ID: 237A 54B1 0287 28BF 00EF 31F4 D0EB 7628 65FC 5E36 Please send encrypted e-mail if possible http://sergiodj.net/